The SOD1 Inhibitor, LCS-1, Oxidizes H2S to Reactive Sulfur Species, Directly and Indirectly, through Conversion of SOD1 to an Oxidase

• Main Authors: Kenneth R. Olson (Author), Tsuyoshi Takata (Author), Kasey J. Clear (Author), Yan Gao (Author), Zhilin Ma (Author), Ella Pfaff (Author), Karthik Mouli (Author), Thomas A. Kent (Author), Prentiss Jones (Author), Jon Fukuto (Author), Gang Wu (Author), Karl D. Straub (Author)
• Format: Book
• Published: MDPI AG, 2024-08-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.

Summary

LCS-1, a putative selective inhibitor of SOD1, is a substituted pyridazinone with rudimentary similarity to quinones and naphthoquinones. As quinones catalytically oxidize H₂S to biologically active reactive sulfur species (RSS), we hypothesized LCS-1 might have similar attributes. Here, we examine LCS-1 reactions with H₂S and SOD1 using thiol-specific fluorophores, liquid chromatography-mass spectrometry, electron paramagnetic resonance (EPR), UV-vis spectrometry, and oxygen consumption. We show that LCS-1 catalytically oxidizes H₂S in buffer solutions to form RSS, namely per- and polyhydrosulfides (H₂S_n, n = 2-6). These reactions consume oxygen and produce hydrogen peroxide, but they do not have an EPR signature, nor do they affect the UV-vis spectrum. Surprisingly, LCS-1 synergizes with SOD1, but not SOD2, to oxidize H₂S to H₂S_3-6. LCS-1 forms monothiol adducts with H₂S, glutathione (GSH), and cysteine (Cys), but not with oxidized glutathione or cystine; both thiol adducts inhibit LCS-1-SOD1 synergism. We propose that LCS-1 forms an adduct with SOD1 that disrupts the intramolecular Cys⁵⁷-Cys¹⁴⁶ disulfide bond and transforms SOD1 from a dismutase to an oxidase. This would increase cellular ROS and polysulfides, the latter potentially affecting cellular signaling and/or cytoprotection.

Item Description

10.3390/antiox13080991
2076-3921